This invention relates to a loading/unloading terminal, especially for use in loading or unloading of petroleum products.
In connection with offshore loading or unloading of hydrocarbons (oil and gas) there has been developed--during the recent years--a special technology called STL technology, wherein the abbreviation STL stands for "submerged turret loading". This technique is based on the use of a special buoy construction consisting of a submerged buoy which comprises a bottom-anchored centre member having a passage for transfer of a flowable medium from or to a transfer line attached to the centre member, and an outer member which is rotatably mounted on the centre member and is arranged for introduction and releasable securement in a submerged downwardly open receiving space at the bottom of a vessel. The outer member of the buoy constitutes a buoyancy member, and when the buoy is not in use it floats submerged at a chosen distance below the sea level, the buoyancy of the buoy corresponding to the weight of the anchoring system of the buoy. In use, the buoy is hoisted up by means of a pick-up line attached to the buoy, and the outer member of the buoy is secured in the receiving space in the topical tanker, for instance a so-called shuttle tanker. The buoy structure allows the vessel during loading/unloading operations to turn about the bottom-anchored centre member of the buoy, under the influence of wind, waves and water currents. Thus, the buoy constitutes a submerged rotating body ("submerged turret"), which has resulted in the above-mentioned designation of the utilized technique.
The STL technique has turned out to have very substantial advantages in practice, both connection and disconnection between vessel and buoy being able to be carried out in a simple and quick manner, even in bad weather with relatively high waves. Further, the buoy may remain connected to the vessel in all weathers, a quick disconnection being able to be carried out if a weather limitation should be exceeded.
As will be appreciated, the use of the STL technique hitherto has been dependent on specially constructed tankers, the STL buoy presupposing a vessel which is provided with a submerged receiving space and the necessary installations for hoisting and introduction of the buoy into the receiving space, for releasable securement of the buoy and for connection of the central passage of the buoy to a pipe system which is arranged on the vessel and communicates with the storage tanks thereof.
It would, however, be desirable to be able to use the STL technique also in connection with tankers which do not have the necessary equipment or are built for the STL buoy, as this will give practical as well as economical advantages, especially with use in smooth and relatively shallow waters.